Sudoku 9981 - description from Softdepia.com:

Sudoku has exploded in popularity over the past few years and sudoku puzzle collections can be found in bookstores everywhere. Soduku is a Japanese logic game. Each Sudoku has a unique solution that can be reached logically without guessing. The rules for solving classic sudoku puzzles are very simple. You need to fill the grid in such a way that each row, column and 3x3 region contains the digits 1-9 using the provided numbers. Sudoku game for Windows,with the color marking function and specific method to control candidate number,you can use the advanced techniques of sudoku more easily. Full version features

Branching to help solve the most difficult puzzles

Candidate number auto fill, with auto update

Enter puzzles from newspapers and magazines.

Show simple candidate

Copy and paste sudoku

Create, save, print, play, and solve sudoku puzzles.

Multiple levels of undo

With the color marking function.

There are different degrees of difficulty.

Print sudoku with six mode.

You can save and replay the whole solving process.

Sudoku 9981 - description from developer:

You can create, play, print,and solve Sudoku puzzles. Sudoku 9981 has unlimited puzzles for you to play, or you can copy puzzles from newspapers and magazines. You can also open many more grids from the Internet. The program will help you out when you get stuck as some of the features included are: automatically generate possible number notes; solve puzzle; highlight where you went wrong.Comprise function of displaying Singles Candidature.Most hard puzzles.The puzzles can be saved as image files.

Sudoku 9981 is a "Free to try" program. You can download and try it for an evaluation period.